Robotic apparatuses, systems and methods

ABSTRACT

A mobile device for traversing a ferromagnetic surface. The device includes a frame and at least one surface contacting device attached to the frame. The device also includes a Halbach magnet array attached to the frame, wherein the Halbach magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface.

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present invention claims priority under 35 U.S.C. 119 to U.S.Provisional Patent Application No. 60/292,948 filed May 23, 2001.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was partially funded by the U.S. Governmentpursuant to NASA Grant No. NCC5-223. The U.S. Government may havecertain rights in this invention.

BACKGROUND

[0003] Robotic devices have become increasingly prevalent in industrialsettings where automation of hazardous, time-consuming, and preciseoperations is desirable. For example, robots have been employed toinspect and repair storage tanks, pipelines, and nuclear facilities, andto strip paint and to apply finishes.

[0004] In paint stripping operations, for example, the process ofmanually stripping paint and other finishes off of large structures suchas storage tanks, ships, and bridges is a labor-intensive process thatis often performed by humans using grit blasting or ultra high pressure(UHP) water jetting techniques and devices. Such techniques and devices,in addition to being labor-intensive, may also create waste disposalproblems because, for example, in the case of grit blasting, the grit isintermixed with paint and coating particles (e.g. fungicides) and thusmust be disposed of in an environmentally-friendly manner.

[0005] Various robotic devices have been developed for use in strippingpaint from large structures. For example, the Flow Hydrocat™manufactured by Flow International Corporation, uses a vacuum to attachto the surface being stripped. The Hydro-Crawler™, manufactured byJetEdge®, uses rigid magnetic tracks that attach to the surface beingstripped and propel the robot on the surface.

SUMMARY

[0006] In one embodiment, the present invention is directed to a mobiledevice for traversing a ferromagnetic surface. The device includes aframe and at least one surface contacting device attached to the frame.The device also includes a Halbach magnet array attached to the frame,wherein the Halbach magnet array provides a magnetic force to maintainthe surface contacting device substantially into contact with theferromagnetic surface.

[0007] In one embodiment, the present invention is directed to a system.The system includes a generator and a mobile device in communicationwith the generator, the mobile device for traversing a ferromagneticsurface. The mobile device includes a frame, at least one surfacecontacting device attached to the frame, and a Halbach magnet arrayattached to the frame, wherein the Halbach magnet array provides amagnetic force to maintain the surface contacting device substantiallyinto contact with the ferromagnetic surface.

[0008] In one embodiment, the present invention is directed to anapparatus for traversing a ferromagnetic surface. The apparatus includesa frame, surface contacting means, and magnetic means attached to theframe, wherein the magnetic means provides a magnetic force to maintainthe surface contacting means substantially into contact with theferromagnetic surface, and wherein the magnetic means is configured inuse to be spaced from the ferromagnetic surface.

[0009] In one embodiment, the present invention is directed to a roboticdevice for operating on a ferromagnetic surface. The device includes aframe, at least one wheel attached to the frame, wherein the wheel has apolymeric coating on a surface that is configured to contact theferromagnetic surface, and a Halbach magnet array attached to the frame,wherein the magnet array holds the wheel in substantially constantcontact with the ferromagnetic surface and wherein the Halbach array isconfigured in use to be spaced from the ferromagnetic surface.

[0010] In one embodiment, the present invention is directed to a mobiledevice for traversing a ferromagnetic surface. The device includes aframe and at least one surface contacting device attached to the frame.The device also includes a magnet array attached to the frame, whereinthe magnet array includes a plurality of magnet bars oriented such thatthe magnet array provides a magnetic force to maintain the surfacecontacting device substantially into contact with the ferromagneticsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further advantages of the present invention may be betterunderstood by referring to the following description taken inconjunction with the accompanying drawings, in which:

[0012]FIG. 1 is a diagram illustrating a robotic device according to oneembodiment of the present invention;

[0013]FIG. 2 is a diagram illustrating a top view of the robotic deviceof FIG. 1 according to one embodiment of the present invention;

[0014]FIG. 3 is a diagram illustrating a side view of the robotic deviceof FIG. 1 according to one embodiment of the present invention;

[0015]FIG. 4 is a diagram illustrating the jet/vacuum system of therobotic device of FIG. 1 according to one embodiment of the presentinvention;

[0016]FIG. 5 is a simplified schematic diagram of an electrical controldevice located on the robotic device of FIG. 1 or located remote fromthe device according to one embodiment of the present invention;

[0017]FIG. 6 is a simplified diagram illustrating a control panel of awireless control device for controlling the robotic device of FIG. 1according to one embodiment of the present invention;

[0018]FIG. 7 is a diagram illustrating a strain relief connector thatcan be used in conjunction with the robotic device of FIG. 1 accordingto one embodiment of the present invention;

[0019]FIG. 8 is a diagram illustrating a system in which the roboticdevice of FIG. 1 may be used according to one embodiment of the presentinvention;

[0020]FIG. 9 is a diagram illustrating a Halbach magnet array accordingto one embodiment of the present invention;

[0021]FIG. 10 is a diagram illustrating the magnetic fields of theHalbach magnet array of FIG. 9 according to one embodiment of thepresent invention;

[0022]FIG. 11 is a diagram illustrating a side view of a magnet used inthe Halbach magnet array of FIG. 9;

[0023]FIG. 12 is a diagram illustrating detection of lift off accordingto one embodiment of the present invention; and

[0024]FIG. 13 is a graph which illustrates the difference between theholding power of a Halbach array and the holding power of aconventional, multi-pole magnet array with iron pole pieces which hasidentical mass.

DESCRIPTION

[0025] It is to be understood that the figures and descriptions of thepresent invention have been simplified to illustrate elements that arerelevant for a clear understanding of the present invention, whileeliminating, for purposes of clarity, other elements. Those of ordinaryskill in the art will recognize, however, that these and other elementsmay be desirable. However, because such elements are well known in theart, and because they do not facilitate a better understanding of thepresent invention, a discussion of such elements is not provided herein.

[0026] Although the present invention is illustrated herein as beingembodied as a robotic device that has paint stripping and removalcapabilities, it can be understood that the principles of the presentinvention may be employed with devices that may perform a variety oftasks such as, for example, spraying finishes, machining, welding, andinspecting surfaces or structures.

[0027]FIG. 1 is a diagram illustrating a robotic device 10 according toone embodiment of the present invention. The device 10 includes ajet/vacuum assembly 12 that can be used for jetting fluids and vacuumingthe fluids and removed particles after jetting. The assembly 12 includesa seal 14, a shroud 16, and ports 18. The seal 14 may be, for example,spring-loaded such that an adequate seal is maintained when the device10 traverses an uneven or obstructed surface. Although the device 10 isillustrated in FIG. 1 as having one jet/vacuum system 12, it can beunderstood that multiple jet/vacuum systems may be included on thedevice 10.

[0028] The device 10 includes surface contacting devices, such as wheels20 that contact the surface that is to be stripped of paints orcoatings. The wheels may be constructed of, for example, a metal such asaluminum with a polymeric (e.g. urethane or polyurethane) coating of,for example, ¼″ thickness. Such a coated wheel provides traction for thedevice 10 but does not mar the surface on which the device 10 isoperating. It can be understood that any suitable type of surfacecontacting device may be used such as, for example, tracks or skids.Actuation devices, such as motors 22, provide power to the wheels 20 toprovide locomotion for the device 10. The motors 22 may be, for example,sealed electric motors compliant with the National ElectricalManufacturers Association (NEMA) 17 standard. However, it can beunderstood that the actuation devices may include, in addition to orinstead of electric motors, a hydraulic or pneumatic drive system.

[0029] The motors 22 are connected via chain drives 24 to differentials26 and the differentials 26 are connected via chain drives 28 to thewheels 20. The differentials 26 may be, for example, limited-slipdifferentials. The chain drives 24 may provide, for example, a 1:1 to2:1 reduction and the chain drives 28 may provide a 2:1 reduction. Thedifferentials 26 may provide, for example, a 3.14:1 reduction. However,it can be understood that the drive system may include, in addition toor instead of chain drives, any of a variety of other devices for powertransmission such as a hydraulic transmission, belt drive or gear drive.

[0030] The device 10 includes a steering system for providing, forexample, four-wheel steering capability to the device 10. A steeringactuator 30 controls a steering linkage 32 that provides directionalmovement of the wheels 20. The steering actuator 30 may provide, forexample, 1200 lbs. of thrust. The linkage 32 may include, for example,pinned connections and the bushings for the steering system may be, forexample, oil-impregnated bushings.

[0031] The device 10 includes an ultra high pressure (UHP) fluidconnection 34 that accepts the fluid to be used for stripping, forexample, water. The device 10 also includes air connections 36 thataccept compressed air that can be used to provide downward force to holdthe jet/vacuum assembly 12 against the surface on which the device 10 isoperating and which can be used for a variety of other functions such asto raise and lower the jet/vacuum assembly 12.

[0032] The device 10 includes lifting/safety rings 38 that can be usedto lift the device 10 in place using, for example, a crane or other liftdevice. One or more safety lines may be attached to the rings 38 toensure that the device 10 does not fall to the ground if the device 10loses contact with the surface on which it is operating.

[0033] In one embodiment, the device 10 is designed to operate onsurfaces that are ferromagnetic, such as storage tanks and ship hulls.The device 10 is thus provided with magnets 40 to adhere the device 10to such surfaces. The magnets 40 may be any type of suitable fixedmagnet or electromagnet. In one embodiment, the magnets 40 are Halbacharrays constructed of, for example, neodymium-iron-boron (NdFeB), thatprovide, for example, 1400 lbs. to 2400 lbs. of pull, as describedfurther hereinbelow. The presence of the magnets 40 allows for thedevice 10 to operate on structures that have inclined or verticalsurfaces and allows for the device 10 to operate in an upside-downposition on, for example, the bottom of the hull of a ship and providesso much surplus holding force that the device 10 can pull heavy loads(such as hoses full of water) vertically up the side of a smoothferromagnetic structure even in the presence of water and oil on thesurface. The magnets 40 may be designed and constructed, as describedhereinbelow, such that the magnets 40 do not wear from contact with thesurface on which the device 10 is operating and so that the magnets 40do not mar the surface on which the device 10 is operating.

[0034] The various components of the device 10, including a frame 42,may be constructed of any suitable material such as, for example,plastic, stainless steel, titanium, aluminum, or coated steel.

[0035]FIG. 2 is a diagram illustrating a top view of the robotic device10 of FIG. 1 according to one embodiment of the present invention. Inaddition to the elements shown in FIG. 1, the device 10 is illustratedin FIG. 2 having vacuum hoses 50, electrical cables 52, safety tether54, and water supply hose 56 attached thereto.

[0036]FIG. 3 is a diagram illustrating a side view of the robotic device10 of FIG. 1 according to one embodiment of the present invention.

[0037] Although the device 10 is illustrated in FIGS. 1-3 as having fourwheels 20, it can be understood that any suitable number andconfiguration of wheels, tracks, skids, etc. may be used depending onthe application for which the device 10 will be used and the desiredhandling characteristics of the device 10. For example, the device 10could be implemented with various three-wheel configurations, four-wheelcart configurations, and four-wheel articulated configurations.

[0038]FIG. 4 is a diagram illustrating a bottom view of the jet/vacuumsystem 12 of the robotic device 10 of FIG. 1 according to one embodimentof the present invention. The system 12 includes the seal 14. The seal14 may be constructed from a flexible material such as, for example,polyurethane, that creates a seal with the surface on which the device10 is operating and allows the device 10 to operate close to obstacles.A rotating spray assembly 60 includes, for example, multiple fluidoutlets. The outlets may be, for example, sapphire spray jets. The sprayassembly 60 may be an assembly sold by, for example, HammelmannCorporation. The vacuum ports 18 carry away spent fluid and debris. Inone embodiment, the jet/vacuum system 12 may be constructed to have a 16inch diameter, although any suitable diameter of the system 12 may beused depending on the desired turning radius of the device 10.

[0039]FIG. 5 is a simplified schematic diagram of an electrical controldevice 70 located on the robotic device 10 of FIG. 1 or remote from thedevice 10 according to one embodiment of the present invention. Thedevice 70 includes a pump relay kill 72 that can stop the operation ofthe jet/vacuum system 12. An emergency stop loop 74 allows the operatorof the device 10 to stop the device 10 in the event of an emergency. Anoperator interface receiver 76 receives operator commands via, forexample, a wireless control device. A control microcontroller 78provides control signals for controlling various systems of the device10. An automation computer 80 provides various automated functions forthe device 10 as described hereinbelow. The computer 80 receives inputfrom, for example, one or more cameras located on the device 10 and agyro tilt sensor.

[0040] A front motor control circuit 82 includes a filter 84 and anamplifier 86 and a rear motor control circuit 88 includes a filter 89and an amplifier 90. A turn actuator circuit 91 includes a filter 92 andan amplifier 93. A jet/vacuum system (head) spin motor circuit 94includes a filter 95 and an amplifier 96 and a jet/vacuum system (head)raise/lower actuator circuit 97 includes a filter 98 and an amplifier99. The amplifiers 86, 90, 93, 96, and 99 may be, for example, EmersonEN208 amplifiers with FM3.

[0041]FIG. 6 is a simplified diagram illustrating a control panel 100 ofa wireless control device for controlling the robotic device 10 of FIG.1 according to one embodiment of the present invention. The controldevice on which the control panel 100 is located may be any type ofcontrol device such as a wireless or a wireline control device. Avehicle speed control dial 102 allows the operator of the device 10 tocontrol the speed of the device 10. A rotate speed dial 104 allows theoperator of the device 10 to control the rotate speed of the device 10and a head height dial 106 allows the operator of the device 10 toadjust the height of the jet/vacuum system 12. An emergency stop button108 allows the operator of the device 10 to stop the device 10 in theevent of an emergency.

[0042] A joystick 110 provides for basic control of the device 10 andallows the operator of the device 10 to easily control the direction ofthe device 10 during operation. A cruise control button 112 enables anddisables an automatic cruise control function of the device 10. Avision/gyro button 114 enables control of the device 10 by a computervision system. A forward/reverse button 116 allows the operator of thedevice 10 to change the direction of the device 10. A water jet button118 allows the operator of the device 10 to start and stop the flow ofwater to the jet/vacuum system 12. An end of row button 120 allows theoperator of the device to cause the automatic, computer-visioncontrolled drive to turn the device 10 around. A right angle turn button122 allows the operator of the device 10 to efficiently cause the device10 to make a right angle turn during operation. A home button 124 allowsthe operator of the device 10 to set the desired center position for thesteering joystick.

[0043]FIG. 7 is a diagram illustrating a strain relief connector 128that can be used in conjunction with the robotic device 10 of FIG. 1according to one embodiment of the present invention. The connector 128may connect to one of the lifting/safety rings 38 via a clip 130. Theconnector 128 relieves the strain on the cables and hoses 52, 56 duringoperation of the device 10.

[0044]FIG. 8 is a diagram illustrating a system 200 in which the roboticdevice 10 of FIG. 1 may be used according to one embodiment of thepresent invention. FIG. 8 illustrates the case where the device 10includes a jet/vacuum system 12 for stripping paint and coatings from asurface using UHP water. A controller 202, on which the control panel100 of FIG. 6 may be located, may be used by an operator to control thedevice 10. The controller 202 may be, for example, a wireless or radiocontrol device. A generator 204, such as an enclosed diesel generator,provides electrical power to the device 10 and various other componentsof the system 200. A water pump 206, such as a diesel water pump,supplies water to the jet/vacuum system 12 of the device 10. A vacuum208, such as an electric vacuum, vacuums spent water and removedparticles via the jet/vacuum system 12 of the device 10. In oneembodiment, the vacuum 208 is a 56 kW vacuum that pulls approximately128 m³ per minute through the jet/vacuum system 12 with a vacuum ofapproximately 38 cm Hg.

[0045] The output of the vacuum 208 enters a settling tank 210 in whichsolid waste settles for removal. The liquid portion of the settling tank210 is directed to a filtration unit 212, such as an enclosed ultrafiltration unit, where solids are filtered. In one embodiment, thefiltration unit 212 includes a centrifuge that removes the solid waste.In one embodiment, the filtration unit 212 includes a sand filter and asecondary filter that is tailored to remove dissolved chemicals that areexpected to be in the water vacuumed from the jet/vacuum system 12. Thefiltered water output from the filtration unit 212 may be recycled inthe system 200 by the water pump 206 or may be returned to theenvironment. In one embodiment, the water output from the filtrationunit 212 is 1 micron filtered water.

[0046]FIG. 9 is a diagram illustrating a Halbach magnet array 220according to one embodiment of the present invention. A Halbach magneticarray is a series of magnets which are so arranged as to simulate amagnetic monopole. The result is a magnetic assembly which, unlike mostother magnetic devices, exhibits magnetic attraction predominately on asingle surface. The Halbach array uses the power of the magnet elementswhich comprise it in an efficient manner to produce a magnetic device ofunusual strength and ability to throw magnetic flux across significantair gaps. A Halbach device might be composed of 4 or more magneticelements with each element having a different axis of magneticorientation. The change in orientation from one element to the next maybe 90 degrees or less. Magnetic elements may be arranged in a straightline, a circular fashion or a variety of other manners to achieve thesame effect. The Halbach array 220 is used for the magnets 40 of thedevice 10 according to one embodiment of the present invention. TheHalbach array 220 includes permanent magnet bars 222 arranged andoriented in such a way that the magnetic field of the array 220, whichvaries periodically in space along the array, is concentrated on oneface of the array 220 and almost canceled on the opposite face (See FIG.10). The magnetic orientation (i.e. 0 degrees, 45 degrees, and 90degrees) of each of the bars 222, according to one embodiment of thepresent invention, is indicated with an arrow. According to oneembodiment of the present invention, each of the bars 222 may be, forexample, 45 MGOe Neodymium (uncoated).

[0047] The array 220 includes 3 array cycles (i.e. 13 bars 220).However, various embodiments may use a differing number of cycles suchas, for example, 1 cycle (i.e. 5 bars 220) or 2 cycles (i.e. 9 bars220). In one embodiment, the x dimension of the array 220 is 6.75 in.,the y dimension of the array 220 is 2 in., and the z dimension of thearray 220 is 8.5 in.

[0048]FIG. 10 is a diagram illustrating the magnetic fields of theHalbach magnet array 220 of FIG. 9 according to one embodiment of thepresent invention. In FIG. 10, the array 220 is included as one of themagnets 40 of the device 10. The wheels 20 of the device 10 contact aferromagnetic surface 224 on which the device 10 is operating. Themagnet 40 does not contact the surface 224 but, rather, due to theorientation of the magnetic fields emanating from the magnet 40 asdenoted by the shaded areas of FIG. 10, the magnet 40 is separated fromthe surface 224 by an air gap 226. The magnet 40 provides the necessaryforce required to hold the device 10 on the surface 224, even though themagnet 40 does not contact the surface 224 and even though there may beone or more layers of paint or coatings on the side of the surface 224on which the device 10 is operating. The magnet 40 likewise providessufficient force to hold the device 10 when the device 10 operates in aninverted (e.g. upside-down) or vertical position. In one embodiment, theair gap 226 is a ⅝ in. air gap. As illustrated in FIG. 10, the magnet 40does not ride on the surface 224 and, thus, the magnet 40 will not marthe surface 224 during operation of the device 10. Because the magnet 40does not contact the surface 224, the device 10 is able to traverseconcave or convex and/or inverted surfaces that contain surfaceirregularities, dents, etc. because the wheels 20 provide the solecontact of the device 10 with the surface 224.

[0049]FIG. 11 is a diagram illustrating a side view of a magnet 222 usedin the Halbach magnet array 220 of FIG. 9. FIG. 11 illustrates twoembodiments of the shape of the bars 222 that comprise the array 220.The first embodiment, designated as 300, presents a curved working faceand the second embodiment, designated as 302, presents a segmentedworking face.

[0050] The Halbach array 200 has many advantages over methodstraditionally used to hold devices on ferromagnetic surfaces such asvacuum attachments, which are unreliable and impede movement of thedevice, magnetic wheels and tracks, which are heavy and which marsurfaces, and conventional magnetic arrays which provide one-third theholding power of a Halbach array for their weight. The high holdingpower of a Halbach array for its weight, and the ability of this type ofmagnet to throw its magnetic field farther than other types of magneticsolutions makes it possible to build a device with unprecedentedperformance on ferromagnetic surfaces.

[0051]FIG. 12 is a diagram illustrating detection of lift off accordingto one embodiment of the present invention. If the magnet 40 starts tolose sufficient force to adhere the device 10 to the surface 224, thesize of the air gap 226 becomes increasingly larger until the wheels 20,and thus the device 10, lose contact with the surface 224. Thus, ifeither the size of the air gap 226 or the magnetic flux at the surface224 can be measured using appropriate sensors located on the device 10,the operator of the device 10 may be alerted that the device 10 is aboutto lose contact with the surface and the operator may take correctiveaction. Alternatively, the device 10 may automatically takeself-correcting action such that the device 10 does not lose contactwith the surface 224.

[0052]FIG. 13 is a graph which illustrates the difference between theholding power of a Halbach array and the holding power of aconventional, multi-pole magnet array with iron pole pieces which hasidentical mass. It can be seen in FIG. 13 that the Halbach arraysolution is very substantially more efficient with any reasonable airgap. This efficiency is what makes a Halbach-equipped device, asdescribed herein, well-suited to operation on vertical and invertedferromagnetic surfaces where high holding power and light weight areessential.

[0053] In various embodiments, the device 10 may be equipped withautomated mobility features that enable the device 10 to be operatedmore efficiently. Such features may be implemented and controlled by theautomation computer 80. One such feature is termed “cut-line trackingcruise control.” This feature may be useful when the device 10 is usedto strip paint or coatings from a surface. During operation, the device10 may make various straight-line passes over an area, with eachsuccessive pass overlapping slightly with the immediately-prior pass.Although such overlap ensures complete coverage of the device 10, itmaybe difficult for an operator of the device 10 to consistently operatethe device 10 with an overlap that is neither too small nor too large.

[0054] The device 10 may thus employ, for example, a forward-lookingcamera that can sense, using, for example, a computer vision algorithm,a cut line that demarcates the area on which the device 10 has operatedfrom the area on which the device 10 has not operated. Such a computervision algorithm may be, for example, an algorithm that relies on acolor histogram-based correlation to find likely cut line points, and anaggressive line fitting algorithm to fit the most likely cut line.Because the device 10 can detect the cut line, the device 10 mayautomatically follow the cut line with little or no operatorintervention.

[0055] Another automated feature is termed the “paint residue cruisecontrol.” This feature may be useful when the device 10 is used to strippaint or coatings from a surface. As the device 10 operates, a slowerspeed may strip more paint or coating and a faster speed may strip lesspaint or coating. Because paint and coating thicknesses may vary fromsurface to surface or from one part of a surface to another, it may bedifficult to operate the device 10 at a uniform speed and effectivelyremove all of the paint or coating. The device 10 may thus employ areverse-looking camera that monitors the surface that is being stripped.The camera may feed images to an algorithm that has been trained from aset of sample images to recognize the statistical color characteristicsof the stripped surface (e.g. bare steel). The algorithm may compute thepercentage of paint or coating left on the surface that has beenstripped and thus the device 10 may be automatically slowed if all ofthe paint or coating has not been removed.

[0056] The systems, methods, and techniques discussed herein allow foran improved device that allows for the use of non-surface marringwheels, provides for better traction on surfaces, provides for bettermaneuverability and obstacle clearing, does not mar or scratch surfaces,and provides a light weight and low cost magnetic assembly that has ahigh magnetic holding power.

[0057] While several embodiments of the invention have been described,it should be apparent, however, that various modifications, alterationsand adaptations to those embodiments may occur to persons skilled in theart with the attainment of some or all of the advantages of the presentinvention. It is therefore intended to cover all such modifications,alterations and adaptations without departing from the scope and spiritof the present invention as defined by the appended claims.

What is claimed is:
 1. A mobile device for traversing a ferromagnetic surface, comprising: a frame; at least one surface contacting device attached to the frame; and a Halbach magnet array attached to the frame, wherein the Halbach magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface.
 2. The device of claim 1, wherein the surface contacting device includes a wheel coated with a polymer.
 3. The device of claim 1, further comprising a motor attached to the frame.
 4. The device of claim 1, wherein the surface contacting device includes one of a wheel, a track, and a skid.
 5. The device of claim 1, wherein the Halbach magnet array does not contact the ferromagnetic surface.
 6. The device of claim 1, wherein the Halbach magnet array includes a plurality of magnetic bars, and wherein the magnetic bars are arranged such that a magnetic force created by the array extends substantially toward the ferromagnetic surface.
 7. A system, comprising: a generator; and a mobile device in communication with the generator, the mobile device for traversing a ferromagnetic surface, wherein the mobile device includes: a frame; at least one surface contacting device attached to the frame; and a Halbach magnet array attached to the frame, wherein the Halbach magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface.
 8. The system of claim 7, further comprising a device controller in communication with the mobile device.
 9. The system of claim 8, wherein the device controller is a wireless controller.
 10. An apparatus for traversing a ferromagnetic surface, comprising: a frame; surface contacting means; and magnetic means attached to the frame, wherein the magnetic means provides a magnetic force to maintain the surface contacting means substantially into contact with the ferromagnetic surface, and wherein the magnetic means is configured in use to be spaced from the ferromagnetic surface.
 11. The apparatus of claim 10, wherein the surface contacting means include at least one of a wheel, a track, and a skid.
 12. The apparatus of claim 10, wherein the magnetic means includes a Halbach magnet array.
 13. A robotic device for operating on a ferromagnetic surface, comprising: a frame; at least one wheel attached to the frame, wherein the wheel has a polymeric coating on a surface that is configured to contact the ferromagnetic surface; and a Halbach magnet array attached to the frame, wherein the magnet array holds the wheel in substantially constant contact with the ferromagnetic surface and wherein the Halbach array is configured in use to be spaced from the ferromagnetic surface.
 14. The device of claim 13, further comprising a steering system attached to the frame.
 15. The device of claim 13, further comprising an actuation device attached to the frame.
 16. The device of claim 13, further comprising: a lifting/safety ring attached to the frame; and a strain relief connector attached to the lifting/safety ring.
 17. A mobile device for traversing a ferromagnetic surface, comprising: a frame; at least one surface contacting device attached to the frame; and a magnet array attached to the frame, wherein the magnet array includes a plurality of magnet bars oriented such that the magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface. 